1. Field of the Invention
The present invention relates generally to material processing, and more particularly, but not exclusively, to methods and apparatus for processing a ferroelectric material.
2. Description of the Background Art
Lithium tantalate (LiTaO3) and lithium niobate (LiNbO3) are widely used materials for fabricating nonlinear optical devices because of their relatively large electro-optic and nonlinear optical coefficients. These nonlinear optical devices include wavelength converters, amplifiers, tunable sources, dispersion compensators, and optical gated mixers, for example. Lithium tantalate and lithium niobate are also known as ferroelectric materials because their crystals exhibit spontaneous electric polarization.
Because lithium tantalate and lithium niobate materials have relatively low bulk conductivity, electric charge tends to build up in these materials. Charge may build up when the materials are heated or mechanically stressed. Because the charge may short and thereby cause a device to fail or become unreliable, device manufacturers have to take special (and typically costly) precautions to minimize charge build up or to dissipate the charge.
The bulk conductivity of a lithium niobate material may be increased by heating the lithium niobate material in an environment including a reducing gas. The reducing gas causes oxygen ions to escape from the surface of the lithium niobate material. The lithium niobate material is thus left with excess electrons, resulting in an increase in its bulk conductivity. The increased bulk conductivity prevents charge build up.
Although the just described technique may increase the bulk conductivity of a lithium niobate material under certain conditions, the technique is not particularly effective with lithium tantalate. A technique for increasing the bulk conductivity of a lithium tantalate material is desirable because lithium tantalate is more suitable than lithium niobate for some high-frequency surface acoustic wave (SAW) filter applications, for example.